The project will use an integrative approach involving the disciplines of Biomechanics, Motor Learning, and Mechanical Engineering to investigate how the human body learns to coordinate mono- and Particular muscles when controlling the direction of external reaction forces arising from contact with the environment. First, fundamental differences in the control of mono- and Particular muscles will be examined by having participants learn a novel force-directing task, consisting of one-legged bicycle pedaling. Changes in muscle activation timing and force direction will be studied. Next, the learning process will be examined more closely by analyzing the data from the learning task using methods from Dynamical Systems Theory. Changes in the coordination of mono- and Particular muscles and the complexity of their activation patterns will be investigated. Finally, the information gained from these experiments will be used to develop a computer simulation of the pedaling task. By manipulating a musculoskeletal model, replacing simulated Particular muscles with equivalent monoarticular muscles, changes in coordination and task accuracy can be investigated. The results of the simulation will be compared with the experimental data to aid in developing a description of how the central nervous system learns to interact with the environment by successfully controlling external forces. This information will be valuable to future research centered on the rehabilitation of patients with neurological diseases or disorders, who must reacquire the ability to control external forces. [unreadable] [unreadable] [unreadable]